A catalyst comprising a titanium compound carried on a magnesium halide in, an active state, is known as a catalyst for use in the production of olefin polymers such as a homopolymer of ethylene or an α-olefin and an ethylene/α-olefin copolymer.
As the catalyst for olefin polymerization (hereinafter, “the catalyst for polymerization” is used sometimes to encompass “catalyst for copolymerization”), a solid-titanium catalyst component comprising magnesium, titanium, halogen, and an electron donor, and an organometallic compound is known.
This catalyst has a high activity, in polymerization or copolymerization of α-olefins such as propylene, and butene-1, similar to polymerization of ethylene (hereinafter, “polymerization” is used sometimes to encompass “copolymerization”), and the stereospecificity of the resulting polymer (hereinafter, “polymer” is used sometimes to encompass “copolymer”.) is also high.
Among these catalysts, a catalyst using a solid titanium catalyst component having an electron donor selected from carboxylates typically phthalates carried there on, an aluminum-alkyl compound as a catalyst component, and a silicon compound having at least one Si—OR bond (R is a hydrocarbon group) is known to exhibit excellent performance.
The present inventors have made investigations for the purpose of obtaining a catalyst for olefin polymerization more excellent in polymerization activity and stereoregularity, and as a result, they found that this object can be achieved by a catalyst using a specific solid titanium catalyst component having magnesium, halogen, titanium and an electron donor (b), and an organometallic compound, or by a catalyst comprising a specific solid titanium catalyst component comprising magnesium, titanium, halogen and an electron donor (b), an organometallic compound, and, an electron donor (c).